Process for low temperature polymerization using a dehydrogenated rosin acid soap



Patented June 29, 1954 PROCESS FOR LOW TEMPERATURE POLY- MERIZATION USING A DEHYDROGENATED ROSIN ACID SOAP Edwin J. Vandenberg, Wilmington, Del., assignor to Hercules Powder Company, Wilmington, Del.,. a corporation of Delaware No. Drawing. Application March 18, 1953, Serial No. 343,256

Claims. 1

This invention relates toan improved process for the polymerization of unsaturated 'compounds. More particularly, the invention relates to a process. for. emulsion polymerization of vinyl, vinylidene, and vinylene compounds at temperatures below 0 C. application is a continuation-in-part of application Serial No. 61,917, filed: November 24, 1948, by: Edwin J. Vandenberg.

It is well known that unsaturated com-pounds, and particularlythose which contain the vinyl group, may be advantageously polymerized in aqueous emulsion. Thus, synthetic, rubberlike materials have been preparedby the emulsion polymerization of diolefins and by the interpolymerization of diolefinic: compounds: with other unsaturates' such as styrene, acrylic acid esters; acrylonitrile, and like materials. Likewise, suchmaterials as polyvinyl halides, polyvinyl acetate, polystyrene, polymethyl methacrylate and var ious: other addition polymersv have been prepared by the emulsion polymerization technique.

The emulsion polymerization of vinyl compounds has customarily'been effected at relativel y high temperatures. For example, a temperature of-about. 122 F; hasbeen accepted as a standard for the commercial production of tlie=butaditene-- styrene copolymer-type synthetic rubbers. Conventional peroxide catalysts such as potassium persulfateor benzoyl peroxide, and fatty acid soap emulsifying agents suchas potassium oleate have normally been employedinsuch polymerization processes; These prior art emulsion polymerization processes are, however, not as advantageous in some respects as are polymerizations carried out at lower temperatures. It isknown, for example, that the synthetic rubberliltematerials producedby emulsion polymerization at temperatures substantially below 122' F. are markedly superior in important physical characteristics such as tensile strength, elongation, flex life, resilience and resistanceto accelera-ted aging to similar materialsprepared' within the conventional temperature ranges.

It has heretofore been deemed impractical, however, to produce synthetic rubberlike materials in commercial quantities by the low temperature emulsion polymerization of vinyl 'compounds. The utilization of such a low temperature process has previously resulted ina very substantial increase in the reactiontimerequiiedto produce a desirable yield of polymeric materials. Even after extended periods of reaction, only relatively low yields of. such polymeric materials were normally obtained. The discovery 2 V of a process whereby the advantages whichattend the low temperature emulsion polymerization of vinyl compounds might be availed of, and a high quality rubbery polymericproduct obtained in good yield after-a reasonable period of reaction has; thereforaconstituted a major problem in the art;

Now in accordance with this invention it has been discovered that the polymerization of or- 0 as antifreeze agent; an u-dialkylarymethyl hydroperoxide as catalyst, an alkali metal dehydrogenated rosin acid salt as emulsifying agent, and an electromotive couple: having a standard oxidation-reduction potential: between about '-1'.0 and about -0.3- volt;

.The standard oxidation-reduction potential to which reference is made herein is. the value in voltsof the electrical. potential of the couple in question determined at25 C. under a pressure of one atmosphere with solutions: of one m'olal' activity referred tozthe potential of the: hydrogenhydrogen ion couple as zero. The: sign of' the oxidation-reduction potential value is negative when. the: reduced form of. the couple: is a weaker reducing agent than, hydrogen.

Oneof the components of the activators of this inventionmay be a metallic reducing agent, and the term metallic: reducing agent? is utilized herein: to designate all of those materials which contain metallic atoms and which are capable of acting as reducing agents, i. e., which are capable of'donating. an electron to other components of the reaction mixture.v Thus;v there is embraced by the term. metallic reducing agent not only the free metallic ions such as. the ferrous ion (Fe but also complexes of such metallic ions: such as the ferrouspyrophosphate complex. Lil'zewise included are metallic compounds which are substantially completely in'-- soluble but which nevertheless act as reducing agents such as, for example, nickel hydroxide Ni (Ol-I)2) which forms the couple the standard oxidation-reduction potential of which is 0..5'volt.

By the process of this invention there may be produced excellent yields of synthetic. rubberlike materials after relatively short periods of reaction. Furthermore, the. rubbery polymers. so

obtained are characterized by superior physical Example 1 Butadiene-1,3 and styrene were copolymerized in a glass container. The reaction mixture was formunlated from the following ingredients in the proportions indicated.

Ingredients: Parts Butadiene- 1,3 72 Styrene 28 Water -1 150 Methanol 50 a,a-Dimethylbenzyl hydroperoxide (catalyst) 0.2 Tertiary Mercaptans (modifier) 0.2

Potassium salt of dehydrogenated rosin (emulsifier) 5.0

FeSOUHQO 0.36 NarPzOmlOHzO (activator) 0.40

"llertiary mercaptan blend composed of C C1 and C1; tertiary mercaptans in the ratio of 3 1 1.

The ferrous pyrophosphate activator was prepared by adding dropwise and with vigorous agitation in an inert atmosphere 200 parts of a solution of 144 parts of ferrous sulfate heptahydrate (FeSOr'lHzO) in 1000 parts of water to 32.0 parts of sodium pyrophosphate decahydrate (NadzOmlOI-IzO) dissolved in 1400 parts of water. When the addition of the ferrous sulfate was completed, the resulting suspension was centrifuged under an inert atmosphere until the ferrous 1 pyrophosphate separated out, the clear supernatant liquid then being decanted and the fer-,

rous Dyrophosphate then being resuspended in a sufficient amount of fresh water so that parts of the activator suspension was equivalent in l iron content to 0.36 part of ferrous sulfate heptahydrate. This activator was stored under an atmosphere of nitrogen at room temperature and was cooled to about 0 0. immediately prior to using.

The potassium salt of dehydrogenated rosin which was employed as an emulsifier was prepared by dissolving 4.52 parts of dehydrogenated rosin in 46.2 parts of methanol in the reaction vessel in which the polymerization reaction was ultimately effected. To this methanol solution of dehydrogenated rosin was added the chemically equivalent amount of 0.5 N aqueous potassium hydroxide. The potassium hydroxide solution was followed by the balance of the 150 parts of water specified in the above recipe with the- I exception of about 10 parts which was reserved for the activator solution. Thus, the emulsifier was obtained in the desired concentration in suspension in a portion of the water-methanol antifreeze medium. The dehydrogenated rosin employed was prepared by the dehydrogenation of a distilled N wood rosin (about 5% light ends and 8% residue removed) in the presence of a palladium-on-carbon catalyst. The product so chtained was characterized by an acid number of 161.

After the emulsifying agent had been prepared. the a,a-dimethylbenzyl hydroperoxide catalyst was dissolved in the balance (3.8 p of the methanol and the resultant solution charged to the reaction vessel. The monomers were then mixed with the mercaptan modifier with the volatile monomer in definite excess and this mixture added to the contents of the reaction vessel. The excess volatile monomer was permitted to vaporize at room temperature to sweep the air out of the reaction vessel. The pressure within the reaction vessel was then adjusted to 30 p. s. i. with nitrogen and the vessel cooled to 0 0., pressured to 30 p. s. i. with nitrogen and then agitated at a temperature of 15 C. for one hour. Ten parts of the previously described activator, which had been cooled to a temperature of about 0 C., was then added and the pressure within the reaction vessel was once more adjusted to 30 p. s. i. with nitrogen. This activator contained the balance of the water specified in the above recipe. After the activator was added, the reaction vessel was again agitated at a temperature of 15 C. for the duration of the reaction period. Samples of the contents of the reaction vessel were withdrawn l6 /2 hours, 22 /2 hours and 41 hours after the addition of the activator. By this means was obtained a known weight of the latex which had been formed after each reaction period. To each latex sample so obtained was added a small portion of 2% aqueous hydroquinone solution to prevent further polymerization from occurring. The latex samples were then dried to constant weight to determine the percentage conversion of the monomer to polymer. Corrections were made for the hydroquinone added and for the nonpolymer solids.

By this means. it was determined that 22% of the monomers had been converted to a rubber-' like copolymeric product after 16.5 hours of reaction, while 34% of the monomers had been so copolymerized after 22.5 hours, and 63% of the monomers had been so copolymerized after 41 hours of reaction.

Example 2 Seventy-two parts of butadiene-l,3 and 28 parts 'of styrene were copolymerized in a manner similar to that described in Example 1. In this case, however, the emulsifying agent was prepared externally from the reaction vessel by heating 4.52 parts of dehydrogenated rosin with the equivalent amount of 2 N potassium hydroxide until a paste soap was formed and then diluting the paste with hot water to form a clear hot soap solution containing the potassium salt of dehydrogenated rosin in 10% concentration. After this soap solution had cooled, 50 parts thereof was charged to the reaction vessel. This emulsifying agent was followed by the balance of the water, with the exception of 10 cc. which was reserved for the activator solution, and by 46.2 parts of methanol. From this point on the polymerization reaction was conducted in exactly the same manner as that described in Example 1. However, in this instance the dehydrogenated rosin from which the emulsifying agent was prepared was freed from neutral bodies by extracting an aqueous alcoholic solution to the sodium salt of the rosin with petroleum ether and acidifying the extracted aqueoussolution of the sodium salt of the rosin aesapas to recover the-rosin. The. resin WfiSrOhfiIdCtBP- ized [byamacid number 1018-1180.

.By thisrmeans 24% f themonomers was .converted to a rubbery rcopol-ymeric material after 16:5.hour-s of'reaction, while 37% of the monomers was so copolymerized :after 22.5 hours of reaction, and 59% of the monomers was so copolymerized after :41 hours of 1 reaction.

" Example 23 The a,u-d-imethyl-p isopropylbenzyl hydroperoxide was prepared by the 'airoxidation of p-' diisopropylbenzene and contained 95.5% of the hydroperoxide.

Example 4 'Thesameprocedure as that described in Example 1 was duplicated. In this case, however, 75parts .of butadiene-lfiand 25 parts of methyl isopropenyl :ketone were copolymerized. .By this means 38% 0f the monomers was .copolymerized after 16.5 .-hours :of reaction, while 52% of the monomers wascopolymerized after 22:5 hours of reaction.

Example 5 Seventy-five parts .of 'butadiene-L3 and 25 parts of acrylonitrile were :copolymerized in a manner similar to that described in Example 1. In this case, however, the emulsifying agent was prepared by dissolving 3.01 parts ofxthe dehydrogenated rosin described in Example 1 and 1.40 parts'of lauric acid in 46.2 parts of themethanol portion of the antifreeze :medium and neutralizing the solution so formed with 0.5 .N-aqueous potassium hydroxide. Also in this case, 10.256 part ma-dimethylep-methylbenzyl hydroperoxi'de was utilized :as a catalyst. This hydroperoxide was prepared by the air oxidation of *p-cymene and contained 85.2% of the hydroperoxide.

By this means 63% of the :monomers was copolymerized after 165 hours of reaction, while 73% of the monomers was copolymerized after 22.5 hours of reaction.

Example 6 Seventy-five parts of butadien'e-lfi and '25 parts of methyl isopropenyl ketone were copolymerized in a manner similar to that described in Example 3. In thiscase, however, the activator was prepared by dissolving "12 parts of potassium pyrophosphate KrPzOv in 300 parts :of water and then adding dropw ise in an inert atmosphere and with vigorous agitation :a solution of 14.4 parts of ferrous sulfate heptahydrate (FSO4.7H20) in '93 parts of water. "The activator so prepared was stored under nitrogen and placed in an :ice chest at 20 *Cruntil utilized.

Likewise in this case, 0.307 parts :of n e-dimethyl-p-isopropylbenzy1 hydroperoxide wasutilized as a catalyst. This mac-dil'IIGllhYl-fD-iSO- propylbenzyl hydroperoxide was prepared by the air oxidation .of p-diisopropylbenzene and contained 95.5% of .the .hydroperoxide.

After 16.5 hours of reaction of the .monomore was copolymerized, while after .41 .hours of 6 reaction 36% of the monomers was copolymerized.

Example 7 Butadiene-1,3 and styrene were copolymerized in a glass container. Thereaction mixture was formulatedfrom the following ingredients in the proportions vindicated:

Ingredients: Parts Butadiene "7 2 Styrene -28 Water "150 Methanol Potassium soap *ofdehydrogenated Rosin 5Z0 Tertiary mercaptans \1 (modifier) 0.20-

' Potassium sulfate 0.20

:Isopropylnaphthalene 'hydroperox- "ide 0J28 -l='eE3O4.'7I-I2(D 0:36 K4P20'z 0.30-

Tertiary mercap'tan blend composed of C12, C and 0 tertiary mercaptans in the ratio of-B :1 1.

The "ferrous 'pyrophosphate activator was pre paredas set forth in Example 6. The'potassium salt of dehydrogenated rosin which was employed as an emulsifier was prepared by adding concentratedpotassium hydroxideto molten dehydro genated rosin at atemperature of 275-300 'C. with vigorous agitation under an inert atmosphere. The paste soap so prepared had a solids contents of 64% and an acid number of 12.3. The dehydrogenated rosinemployed was 'prepared by the dehydrogenation of an N wood rosin in the presence of a palladium-on-carbon catalyst. The product'so obtained was characterized by an acid number of 160. The paste so prepared was diluted with all of the formula methanol except for "7.9 parts which was added with the initiator and after the water. An amount of 0.52 N'aqueous potassium hydroxide equivalent to the acid number of the soap was added and then all-of the formula water, except for that "in the activator, was "added. The soap was charged to the reaction vessel.

After the emulsifying agent had been prepared, 'the isopropylnaphthyl hydroperoxide catalyst was dissolved in the balance of the methanol, and the resultant solution charged to the reaction vessel. The remainder of the polymerization procedure was as set forth in Example 1.

By this means it was determined that of the-monomers had been converted to I a ruloberiike copolymeric product after 40 hours of rear:-

ion.

. Example 8 seventytwo parts o'f butadienelj and'2-8 parts of styrene were copolymerized in a manner similarto that described in Example 7; In thiscase, however, :diisopropylbenzene monohydroperoxide was used instead "of "isopropylnaphthlene hydroperoxide. The sactivator was prepared with half theamount of water specified in Example -6 and the emulsifying agent consisted of a mixture of 87% of the potassium soap of dehydrogenated rosinnpreparedas described in Example 7 together with 13% .of :a mixture of palmitic and stearic acids. This combination :of dehydrogenated rosin soap :and fatty acid soap was :diluted with all of the formula methanol except !for 7.9 parts which was added with the initiator and after the water, and then rsufilcient 0.25 [N aqueous potassium hydroxideequivalent to .thefacid number of the soap was added, and then all of the formula wa'-' ter except for that in ,the activator was added. This soap was charged to the reaction vessel. After 24 hours of reaction, it was determined that 85% of the monomers had been converted to a rubberlike copolymeric product.

The dehydrogenated rosin acid emulsifying agents with which this invention is concerned include the alkali metal salts of dehydrogenated rosin or of dehydroabietic acid and mixtures of these salts with fatty acid soaps. Relative to any of these emulsifying agents it is preferable to use the potassium salt. Dehydrogenated rosin is also known as disproportionated rosin. The dehydrogenated rosin from which these emulsifying agents are formulated may be prepared by contacting gum or wood rosin or rosin-containing materials at an elevated temperature with an active hydrogenation catalyst in the absence of added hydrogen. Catalysts such as palladium, platinum, nickel, copper chromite, etc., are suitable. The catalyst may be supported on a carrier, such as granular alumina, fibrous asbestos, or activated charcoal. Dehydrogenation or disproportionation with a palladium catalyst, for example, may be conducted either by a batchwise or continuous procedure. Thus, the rosin may be agitated with about to about by weight of a palladium catalyst supported on activated carbon (1 to 2% palladium) at about 150 C. to about 300 C. for about 1 to about 5 hours. In the continuous process, the molten rosin flows over the supported palladium catalyst at a temperature Within the range of about 225 to about 300 C. to provide a contact time of about /4 hour to about 1 hour.

It often is advantageous to refine the whole rosin prior to its dehydrogenation or disproportionation, and the same is true as applied to the whole dehydrogenated or disproportionated product. Prior to its dehydrogenation or disportionation the rosin may be refined by crystallization, by means of a selective solvent such as furfural or phenol, or by an absorbent earth.

With absorbent earths, such as fullers earth or Percol, Percol being a special grade of hentonite which has been treated with sulfuric acid, the rosin may be refined by contacting a gasoline solution of the rosin with the earth, either batchwise or by passing the solution continuously through a column packed with the absorbent. The rosin solution is kept under an atmosphere of carbon dioxide or other inert gas throughout the refining procedure, and, after being filtered, is distilled to remove the solvent. The color of the rosin is improved by this procedure, and, after dehydrogenation or disproportionation, the product gives improved yields of vinyl polymerizates when used in accordance with this invention.

The whole dehydrogenated or disproportionated rosin also may be refined, as by distillation, heat treatment, alkali extraction, precipitation, etc. The heat treatment of dehydrogenated or disproportionated rosin may be carried out either in vacuum or in the presence of an inert gas, such as nitrogen or carbon dioxide, by heating the rosin material at a temperature between about 220 C. and about 270 C. for about 2 to about 15 hours. Utilizing vacuum, the temperature preferably is between about 220 C. andabout 240 C., while in the case of an inert atmosphere it is between about 240 C. and about 260 C. The heat treatment may be combined with the dehydrogenation or disproportionation re- 8 action by correlation of the desirable conditions for each process. By utilizing a heat treatment, the activity of the dehydrogenated or disproportionated rosin, when used in the form of its alkali metal salts as an emulsifier for vinyl polymerizations, is increased.

In refining dehydrogenated or disproportiom ated rosin by means of an alkaline extraction the rosin is dissolved in a suitable solvent, such as gasoline, and the resulting solution agitated vigorously with an aqueous alkali, such as sodium hydroxide, resulting in the formation of an emulsion stable at room temperature. The concentration of the alkali should not be above 4% and the extraction is carried out only once. Cooling the emulsion causes it to break into two layers, and from the aqueous layer is obtained de-' hydrogenated or disproportionated rosin acids in' yield based on the total acids (88% based on the total rosin treated) and having an acid number of -186. The acids, in the form of their alkali metal salts, give high yields in the emulsion polymerization of vinyl compounds.

Similar to the above procedure is a refining method which involves precipitation of the alkali metal or ammonium salts of dehydrogenated or disproportionated rosin. The rosin is dissolved in acetone, ethanol, isopropanol, or petroleum ether and the resulting solution treated with an alcohol solution of an alkali, such as sodium hydroxide. The use of isopropanol as the solvent and alcoholic sodium hydroxide as the alkali is preferable. The sodium salts of the dehydrogenated or disproportionated rosin acids precipitate immediately and are separated from the solution by filtration. The product is a uniform, very white, fairly dense powder which is useful as the emusifying agent in accordance with this invention.

Another refining procedure applicable to the rosin prior to its dehydrogenation or disproportionation and also to the dehydrogenated or disproportionated product involves the precipitation of the rosin acids as the insoluble salts of certain organic amines, namely, hydroaromatic amines having at least one fully saturated cyclic nucleus, aliphatic amines, aliphatic hydroxyamines and polyalkyl polyamines. The rosin material is dissolved in a suitable solvent such as acetone, isopropanol, Hi-Flash naphtha or gasoline, and the resulting solution is treated with organic amines such as cyclohexylamine, tetraethylene pentamine, 2-amino-2-methyl-1-propanol and diethylamine. The aminesalts precipitate at once and are separated from the solution by filtration or centrifugation. Decomposition of the amine salts with heat or acid regenerates the free acids.

As previously indicated, the dehydrogenated rosin soaps may be utilized in conjunction with fatty acid soaps as emulsifying agents in the process of this invention. Thus, emulsifying agents containing up to 50% fatty acid soaps by weight may be utilized. A preferable range of concentration of fatty acid soaps is from about 10% to about 30% of the weight of the emulsifying agent. It is preferable that the fatty acid soaps employed in this invention be prepared from long chain fatty acids which have from about 12 to about 18 carbon atoms in the molecule. A readily available source of such a mixture of fatty acids and rosin acids is tall oil. Tall oil is a by-product from the manufacture of paper pulp by the digestion of wood with alkaline liquors such as alkaline solutions of sodium sulaeeaisee .93 fide. C'ru'detalll oil consists of a mi Xtur-eof resinand fatty acids in roughly equal proportions in conjunction with minor amounts of neutral, unsaponifiable materials consisting primarily of plant sterols.

Tall oil may generally be dehydrogenated by the sameprocesses as. those previously. described for the dehydrogenation of rosin. It often advantageous. to. refine the tall oil prior. to. dehydrogenation. Various. methods' such as those previously described for. the refi'ningof'rosin are satisfactory and yield products which are substantially lighter in. color than the crude tallloili and. whichare more nearly odorless. Such re.- fined. tallloil's may or may not differ greatly in composition. from the crude material depending. upon. the conditions used. Distillation; for" errample,.may be carriedoutli'nsuch a mannerthat' it-Qis. possible. to separate. a fraction consisting almost exclusively offatity. acids and other'fractions, consisting predominantly of" rosin acids; For. utilization in the preparation of the emulsifying agents of; this invention, however; it is usually desirable that t'alloilbe distilledtoeff'ect separation. only of certainihigh boiling constituentsrwhich. are normally presentand which exert inhibitory effects on both the dehydrogenation andpolymerization processes. By this procedure theratio of. rosin acids to fatty. acids. remainsessentially unchanged; Fractionation into the substantially pure fatty acid. androsinacidconstituents by suchdistill'ation is unnecessary; The distillation should be carried out at reduced pressure, for example,,from about'035 to about-25'" mm. of. mercury. The distillation temperatures" which. are operable within these pressure ranges' will. vary from about 150 C; to" about 300" C.

Althoughthose materials in tall oil which exhibit an. inhibitory effect upon polymerizationreactions can be at. least partially removedby' distillation or other refining. procedures, it is' preferable to remove them by pretreating'thetall oilwith a. spent catalyst resulting from previous tall' oildehydiogenations. Spent palladium and" nickel catalysts" are particularly useful .in' such a" treatment and the refined tall" oil can thenb'e'. dehydrogenated' more readily" than the" crude product. may be carried out under the same conditions as. those used in the dehydrogenation step;

The. dehydrogenatedrosih, dehydro'a'bietic acid andmixturesof these materials with fatty acidsmaybe neutralized with basic cmpounds.of",tl'i'e alkali metals such as hydroxides andlca'rbonat'es" of sodium and'potassium to produce the emulsifying agents of this invention; Theseemulsify= ing agents may be prepared'either in'situ in the reaction vessel in which the polymerizationiis effected or externally therefrom. Inany'eventj. it is. preferable that the emulsifying agent be" admired with the other reactants in theform offa. solution or suspension in a portionof'the antifreeze. medium. in' which" the polymerization is carried out. These emulsifying agents-are preferably prepared" by adding an aqueous-'solu tion of the alkali metal compound utilized'to a solution of the dehydrogenated rosin acidma terial in=a -water'-soluble organicrcompound; such: as methanol, which may constituteza portion of the antifreeze medium; which the... emulsioni.

polymerization reactionisv effected; However; the emulsifying agent maybeprepared by re The. pretreatmentwith spent catalysts;

iii least about 20% solids? Whilethis broad-f range is technicall'y operable; it is preferred forreasons tion mixture; with a Water-soluble organiccoimpound which constitutes a portion oh the antifreeze agent used in preparing the antifreeze mediuma If' desired; the: alkali -metah salts of acting an aqueous solution of thealkali metal'- t compound with the dehydrogenated rosini acid the-dehydrogenated rosin acid-material may; of.

c'ourse;-be=mi xed with preforn'iedfatty acid soaps toproduce suitable emulsifying' agents for use inthe process of" this invention.

Regardless of themethod by whichtheemulsif y-ing agent is prepared; it is desirable; that the dehydrogenat'ed rosin or dehydrogenatedi rosin acids or mixtures-thereofwithi fatty acids which are emplbyed be reacted? with. about: thechemioally equivalent: amount of basic alkali metal compound: Thatis; it isdesirablethat the=emul:-- sify-in'g agent constitute an essentially neutral product containingno substantial excess of either alkalilor: dehydrogenated: rosin: acid. or fatty. acid.

The; emulsifying agents hereinbefore described-1 may be employed: in an amount equivalent to fro1n about-0.-5 to ab'cut15:%: basedonthe total emulsion polymerization: reaction v mixture; A

preferred range on this basis is from about" 1% to about. 2% of the weight. of: the reaction mixture.

The: concentrationiofthe emulsifying agentflin the aqueous phase may. be'from" about V1% to' about; 5%, preferably" fromabout 2% to about 3% Based onath'e weight of the'monomers orig.- inally. presenamthe" emulsifying agent may: be utilized in. an. amount: equivalent to from about to:15=% thereof: andpreferably in anamount equivalent to from about 4% to about 6% of the weight thereof;

The: utilization of dehydrogenatedrosin acid soaps" as emulsifying agents" in the. polymerization"..-0f vinyl :compounds is desirable in' that-the. polymers thereby produced are. characterized by. superior: physical properties, particularly in. the

case of rubbery olymer-s. These dehydrogenated rosinisoapiemulsifying agents'are particularly desirable inflow. temperature emulsion polymerization reactions-for the reason thatlthese emulsifying; agents reduce thetendency of the reaction 50; mixture:- to' gel as the'temperature. is lowered Furthermore, these unique and desirable. advantages-.sobtain whenrt'he. dehydrogenated rosin soaps are:employed inconjunction with'fatty acidsoaps asrissthecase, for examp1e,.when the emulsifying agents are prepared. fromhehydifogenated t'alloill The-activators. which are operable in the process-of this invention comprise those. electrom'otive couples having. a standard; oxidation-reduction potential between about -1.'() and" about 0.3

volt, preferably between about 08'andabout 0'E5 volt. Such activators should becapa'bleof' reducing the a,a-dialkylarylmethylhydroperoxide catalyst to a. corresponding aromatic ketone in better than" about'25i'%" yield, for example; 0600- di'methylbenzyl hyd'roperoxide to acetophenone; in from about 0I25hou1 to about BOhours. Pref erable arethose electromotive couples containing a metallic.reducing...agent, such as the'ferrous .(ee.++) ion, which formsa .couple in the reaction mixture. with. an. analogous. material: of higher oxidation state, such-as theferric. ee+++ ion.

Thus,.suitable activators for usein this invention. may: be1.prepared:by addingT-an aqueous: solution material to forrman aqueous .pastecontaining;ativ wot::ferroustsulfate-gheptahydrate FeSOMH Oi with agitation in an inert atmosphere to an aqueous solution of sodium pyrophosphate decahydrate (NaaPzOmlOI-IzO). When the addition of the ferrous sulfate is completed, the ferrous pyrophosphate activator formed may be washed, for example, by centrifuging the reaction mixture to collect the ferrous pyrophosphate, decanting the supernatant liquid, and. resuspending the ferrous pyrophosphate in pure distilled water, The ferrous pyrophosphate should be maintained under an inert atmosphere to prevent the air oxidation thereof and may be cooled to a temperature of about C. prior to incorporation into the low temperature emulsion polymerization system with which this invention is concerned.

Suitable activators may be prepared in like manner from potassium pyrophosphate. The activators so prepared are advantageous in that the ferrous pyrophosphate formed may be utilized without the washing which is desirable in the case of a similar activator prepared from sodium pyrophosphate. Thus, the crude reaction mixture resultant from the addition of the ferrous sulfate solution to the potassium pyrophosphate solution may be employed. However, the activator prepared in this manner is subject to rather rapid deterioration at room temperature, and, accordingly, should be stored at a temperature of about 0' C. or lower.

Insofar as the preparation of ferrous pyrophosphate activators is concerned, the pyrophosphate compound and the ferrous salt utilized should be employed in such proportions that there is present in the reaction mixture in which the activator is formed from about 0.3 to about 2.5 chemical equivalents of the pyrophosphate for each chemical equivalent of the ferrous salt. A preferable range is from about 0.8 to about 2.0 chemical equivalents of pyrophosphate per chemical equivalent of ferrous salt. Particularly desirable is the presence of about 1.4 chemical equivalents of pyrophosphate for each chemical equivalent of ferrous salt. Soluble ferrous salts other than ferrous sulfate, such as for example, ferrous chloride, may, of course, be utilized in the preparation of the ferrous activators which are operable in the process of this invention. Likewise, similar salts of analogous metals may be employed. It is necessary, of course, that the metallic ion component of these salts be in a reduced oxidation state. Furthermore, the ferrous and analogous metallic ions derived from these salts may be complexed with anions other than the pyrophosphate ion to form operable activators. For example, gluconate and citrate ions may be so utilized. The ferrous complex of ethylenedinitrilotetraacetic acid is also operable.

The activator may be used in such an amount that there is provided from about 0.1 to about 3.0 electrons for each hydroperoxy radical. A preferable range for freshly prepared activators is from about 0.8 to about 1.0 electron per hydroperoxy radical, and that for activators aged at room temperature or by heating for a short time at elevated temperatures is from about 0.8 to about 2.0 electrons per hydroperoxy radical.

The catalysts which are operable in the polymerization process of this invention have been 11- lustrated in the examples by c,a-dimethylbenzyl, a,a-dimethyl-p-methylbenzyl and a,a-dimethylp-isopropylbenzyl hydroperoxides. Such hydroperoxides are generally known as a,a-dialkylarylmethyl hydroperoxides, and they may be prepared by the oxidation of alkyl-substi-tuted aro- 12 matic organic compounds having the structural formula R: Ar

in which R1 and R2 represent alkyl groups and Ar represents a substituent selected from the group consisting of aryl and alkaryl groups. The oxidation may be carried out in the liquid phase utilizing air or molecular oxygen as the oxidizing agent. A preferred method of preparing these hydroperoxides involves the liquid phase oxida- 15 tion of the alkyl-substituted aromatic organic compounds having the above structural formula by passing an oxygen-containing gas through the compounds at a temperature between about 25 C. and about 95 C. in the presence of an aqueous alkali. The concentration of the aqueous alkali may be between about 1% and about 35% although it is preferable to use concentrations of about 2% to about 8%. Vigorous agitation is desirable during the oxidation reaction.

As illustrative of the alkyl-substituted aromatic organic compounds which may be oxidized, pcymene, cumene, and diisopropylbenzene may be mentioned. These compounds lead to a e-dimethyl-p-methylbenzyl, 0:,0L-dllll8lihY1bBHZY1, and

o u-dimethyl-p-isopropylbenzyl hydroperoxides,

respectively. Also, in the case of diisopropylbenzene, a,e,e,'a-tetramethyl-p-xylylene dihydroperoxide may be formed. These compounds also may be named as aryl(dialkyl)methyl hydroperoxides, for example, c,a-dimethylbenzyl hydroperoxide may be designated as phenyl(dimethyl) methyl hydroperoxide. The aryl and substituted aryl groups need not be derived from benzene, as is the case in the aforementioned 40 compounds, for compounds containing aromatic nuclei derived from naphthalene, anthracene, phenanthrene, and the like, also are operable when dissolved in a suitable solvent during the oxidation. The aryl roup may be substituted with alkyl groups such as methyl, ethyl, propyl,

isopropyl, butyl, isobutyl, tertiary butyl, and the like, the same alkyl groups also being representative of R1 and R2 in the structural formula. R1 and R2 may be either the same or different.

The amount of hydroperoxide which may be used in accordance with this invention may be between about 0.5% and about 20% based on the amount of solid emulsifying agent used. The preferable amount of hydroperoxide on this basis, however, is from about 2% to about 6%. Based "on the monomers, the amount of hydroperoxide may be from about 0.001 to about 5.0%, a desirable range being from about 0.02% to about 1.5%, and the preferable amount of hydroperoxide on this basis being from about 0.1% to about 0.6%.

6 Aqueous solutions of water-soluble organic compounds of low freezing point may be employed as antifreeze media in the process of this invention. Thus, water solutions of the lower skilled in the art will be able, to select or formualkanols, such as methanol and ethanol, may be.

I a-ecasas 1 3 late :azreactionlmediom, the. fireezing point at which is belowthetemperatureat which itis desiredvto effectaparticular olymerization reaction. -Such reactions may be readily carried out at= temperatures of C. ina medium consisting of 3 parts: of water and 1- part methanoli- As previously indicated, it isadvantageous prior to admixing the emulsifying agent withthe other ingredients ofthe polymerization" system to form a-sol ution or suspension thereof in a portion ofthe anti-fireezemedium.

a-Hydroxy carbonyl compounds or compounds which react as c-hydroxy carbonyl compounds may be added-to the otheringredients of the reaction mixture in the process of this invention. Thus, such compounds as fructose, glucose-,lactose; 1 sorbose; -a'cetylacetone, ascorbic acid, benzoi n, acetoi n, I propionoin; butyroin, isobutyroin, pi-valoin,--and the like; maybe-utilized. In genera those aldehydes andketones containing a hydrox-yl group on an adjacent carbon atom in an alkyl -chanrand having thereby in common tha structural 'groun Q are.operable .m this invention The, preferable a-hydizoxy .aldehydes. and ketones are those. compounds which are known as reducing sugars.

Exemplary. of. thereducing sugars. which may housed. in. accordance with. this invention-are the monosaccharides, mcluding. aldotrioses such as glycerose;v ketotri'oses such. as dioxyacetone aldotetroses. such as erythrose. and. threose; ketotetroses such as erythrulose;aldopentoses. uch as 3 arabinose, xylose, Iyxose, andtribose ketopentoses such as,. ar.ab.oketosel.and xyloketose; aldohexoses such as. glucose, galactose, mannose,. gulose,. idose,. talose, allose, and the.l'ike;. ketohexoses such. as. fructose .or levulose,.' sorboseandthe like; and otherreducing. sugars including. the disaccharides and.trisaccharidesrsuch as ma ltos.e,,lactose, and. mannotriose. Also operable is the. equimolecular mixture of, fructoseand glucoseobtainedthrough thehydrolysisof sucrose and known as invert sugar. As illustrative of theuw-hydroxycarbonyl compounds, in general, the. amountoiv reducing. sugar ,empl'oyedlmay varyfrom about 0.011% to about 6% of the Weight. of. the monomers. A preferable range on this basis is from .about 0.1% to about 8%.. Particularly appropriate that quantity of sugar equivalent to about 0.5% of the weight of'the monomer.

It isvdesirable, particularly inthepolymerizati'on ,of those compoundsleading. to synthetic rubherlike. materials that there be included in the polymerization reaction, mixture. 2. modifying agent. be used in the process: on? this'iinvention. Thus, the mercaptans normally s0 employed may be utilized, and the amount may be that usually used, for example, in the preparation of synthetic rubbers. It is desirable, however, that the mercaptan modifier be tertiary for the reason that improved modification of the rubber is thereby obtained. Primary mercaptans may, however, be employed if desired' It is of significance, however, that by the process of this The conventional modifying agents may invention there may be produced benzene-soluble,

1'4 resulted in formation of insolubl'etpolymersyand copol ymers. 'I-he unmodified conjugated butadiene polymers and copolymers of this invention are valuable as adhesives, paper-treatingagents and-thelike. l

The emulsion polymerization of the vinyl, vinylene and vinylidene compounds may-be effected accordance: with: thismventionat temperatures up to about- 0 C. Temperatures as low as -'70 C. may-be employed-ii desired. The prefierabl'etemperaturerange isfrom about -30' toabout -5 C;

If desired, small -quantities of inorganic salts su'c-has potassium sulfate may be added tic-the reaction mixture to: reduce the viscosity of the l-a-ti -:esof the polymers obtained. The utilization ofl'arge quantitiesof such-salts, however;--adversely affects the rate-andextent of polymerization, A preferable range of concentration of-such salts 'is'from about 0.'l% to about 0.5% of the Weight of themonomers. Except as otherwise indicated, the conventional emulsion polymeriza tion techniques, concentrations'of reactants and reaction conditions maybe utilized inpracticing the process of this invention.

Compound-sw-h-ich 1naybe advantageously polymerized antifreeze media by the process of this invention includethe' conjugated butadienes suchas butadiene-1 ,3, isoprene; -2,3-dimethyl butadiene-l'fiy chloroprene, piperylene,

monomer mixtures of two or more of thesecon jugated butadienes such as a 'mixtureof butadiene-1 ,3 and 2,3-dimethyl'butadiene-1,3 and monomer mixtures of one'or more of these conjugated butadienes with vinyl compounds-such as styrene, p ch'lorostyrene, p-meth-oxystyrene; vi-nyi naphthalene, acrylic acid, -methacrylonitri'1e, methyl -methacrylate,--methy1 acrylate; -methyl vinyl ketone, methyl isopropenyl 'ketone, methyl vinyl ether andthe-l-ike. The process of this invention is particularly applicable to the preparation of the copolymers of butadiene and styrene oracryl'oni-trile; isoprene and styrene oracrylonitrile, and other rubberlike copol'ymers as'well as'in thepreparation of polymers such as polyvinyl chloride, polyvinyl acetate, polystyrene, polymethyl methaorylate;v polyvinylidene chloride, polyvinyl pyridine, and the various other addition polymers which may be prepared by the emulsion technique;

It has been recognized-by the art that superiorrubber-like material might be preparedirom' vinyl, 'vinylene and vinyli'dene compounds by emulsion polymerization at low temperatures. Heretofore, however, such processes have been found to entail unduly long reaction periods and to result in low yields of polymeric materials. The process of this invention, utilizingas emulsiiying agents the alkali-metal salts of dehyd'ro-* 'genated-rosinacids, permits the attainmentof satisfactory yields of superior polymeric materials in reasonable lengths of time. The combination of the particular catalysts, namely, the a,a-dialkylarylmethyl hydroperoxides, with the particular activators and emulsifying agents results in good yields of polymers from low temperature polymerizations, and particularly in the case of the rubberlike polymers, such as those derived from the copolymerization of butadiene and styrene, imparts desirable physical properties to the polymers,

What I claim and desire to protect by Letters Patent is:

1. In the process which comprises polymerizing an organic compound containing the CH2=CH group at a temperature between about 5 C. and '70 C. in aqueous emulsion in the presence of a water-soluble organic compound of low freezing point as antifreeze agent, an u,u-dialkylarylmethyl hydroperoxide as catalyst, between about 0.5% andabout 5% of an alkali metal salt of a dehydrogenated rosin acid as emulsifying agent, and a metal electromotive couple having a standard oxidation potential between about l.0 and about 0.3 volt as activator, the improvement which comprises using an alkali metal salt of a dehydrogenated rosin acid which is produced by saponifying saiddehydrogenated rosin acid with an aqueous solution of the alkali metal compound to form an aqueous paste soap containing at least about solids, and diluting the said paste prior to admixture with the other ingredients of the reaction mixture with at least a portion of the antifreeze agent.

2. In the process which comprises polymerizing an organic compound containing the CH2=CH group at a temperature between about 5 C. and -70 C. in aqueous emulsion in the presence of a water-soluble organic compound of low freezing point as antifreeze agent, an a,e-dialkylarylmethyl hydroperoxide as catalyst, between about 0.5% and about 5% of an alkali metal salt of a dehydrogenated rosin acid as emulsifying agent, and a metal eleotromotive couple having a standard oxidation potential between about l.0 and about 0.3 volt as activator, the improvement Which comprises using an alkali metal salt of a dehydrogenated rosin acid which is produced by saponifying said dehydrogenated rosin acid with an aqueous solution of the alkali metal compound to form an aqueous paste soap containin from about 50% to about 80% solids, and diluting the said paste prior to admixture with the other ingredients of the reaction mixture with at least a portion of the antifreeze agent.

3. The process according to claim 2 wherein the electromotive couple activator has a standard oxidation potential between about 0.8 and about 0.5 volt.

4. vA process according to claim 2 wherein the catalyst is an a,a-dimethylbenzyl hydroperoxide.

5. A process according to claim 2 wherein the catalyst is an a,a-dimethyl-pmethylbenzyl hydroperoxide.

6. A process according to claim 2 wherein the catalyst is an a,a-dimethyl-pisopropylbenzyl hydroperoxide.

1.,The process according to claim 2 wherein the organic compound containing a CH2=CH group is butadiene-L3.

8. In the process which comprises copolymerizing a mixture of butadienel,3 and styrene at a temperature between about 5 C. and '70 C. in aqueous emulsion in the presence of a watersoluble organic compound of low freezing point as antifreeze agent, an a,a-dialkylarylmethyl hydroperoxide as catalyst, between about 0.5% and about 5% of an alkali metal salt of a dehydrogenated rosin acid as emulsifying agent, and a metal electromotive couple having a standard oxidation potential between about 1.0 and about 0.3 volt as activator, the improvement which comprises using an alkali metal salt of a'dehydrogenated rosin acid which is produced by saponifying said dehydrogenated rosin acid with an aqueous solution of the alkali metal compound to form an aqueous paste soap containing from about 50% to about 80% solids, and diluting the said paste prior to admixture with the other ingredients of the reaction mixture with at least a portion of the antifreeze agent.

9. In the process which comprises copolymerizing a mixture of butadiene-1,3 and acrylonitrile at a temperature between about 5 C. and '70 C. in aqueous emulsion in the presence of a watersoluble organic compound of low freezing point as antifreeze agent, an u,a-dialkylarylmethyl hydroperoxide as catalyst, between about 0.5% and about 5% of an alkali metal salt of a dehydrogenated rosin acid as emulsifying agent, and a metal electromotive couple having a standard oxidation potential between about 1.0 and about -0.3 volt as activator, the improvement which comprises using an alkali metal salt of a dehydrogenated rosin acid which is produced by saponifying said dehydrogenated rosin acid with an aqueous solution of the alkali metal compound to form an aqueous paste soap containing from about 50% to about 80% solids, and diluting the said paste prior to admixture with the other ingredients of the reaction mixture with at least a portion of the antifreeze agent.

10. In the process which comprises copolymerizing a mixture of butadiene-1,3 and styrene at a temperature between about 5 C. and C. in aqueous emulsion in the presence of a watersoluble organic compound of low freezing point as antifreeze agent, an e,a-dirnethyl-p-isopropylbenzyl hydroperoxide as catalyst, between about 0.5% and about 5% of an alkali metal salt of a dehydrogenated rosin as emulsifying agent, and a metal electromotive couple having a standard oxidation potential between about -0.8 and -0.5 volt as activator, the improvement which comprises using an alkali metal salt of a dehydrogenated rosin acid which is produced by saponifying said dehydrogenated rosin acid with an aqueous solution of the alkali metal compound to form an aqueous paste soap containing from about 50% to about solids, and diluting the said paste prior to admixture with the other ingredients of the reaction mixture with at least a portion of the antifreeze agent.

No references cited. 

1. IN THE PROCESS WHICH COMPRISES POLYMERIZING AN ORGANIC COMPOUND CONTAINING THE CH2=CH$ GROUP AT A TEMPERATURE BETWEEN ABOUT -5* C. AND -70* C. IN AQUEOUS EMULSION IN THE PRESENCE OF A WATER-SOLUBLE ORGANIC COMPOUND OF LOW FREEZING POINT AS ANTIFREEZE AGENT, AN A,A-DIALKYLARYLMETHYL HYDROPEROXIDE AS CATALYST, BETWEEN ABOUT 0.5% AND ABOUT 5% OF AN ALKALI METAL SALT OF A DEHYDROGENATED ROSIN ACID AS EMULSIFYING AGENT, AND A METAL ELECTROMOTIVE COUPLE HAVING A STANDARD OXIDATION POTENTIAL BETWEEN ABOUT -1.0 AND ABOUT -0.3 VOLT AS ACTIVATOR, THE IMPROVEMENT WHICH COMPRISES USING AN ALKALI METAL SALT OF A DEHYDROGENATED ROSIN ACID WHICH IS PRODUCED BY SAPONIFYING SAID DEHYDROGENATED ROSIN ACID WITH AN AQUEOUS SOLUTION OF THE ALKALI METAL COMPOUND TO FORM AN AQUEOUS PASTE SOAP CONTAINING AT LEAST ABOUT 20% SOLIDS, AND DILUTING THE SAID PASTE PRIOR TO ADMIXTURE WITH THE OTHER INGREDIENTS OF THE REACTION MIXTURE WITH AT LEAST A PORTION OF THE ANTIFREEZE AGENT. 